My 89 560 SEC with 124,000 when driving at 60 MPH for about 1 hour will drop down a gear 15-30 minutes later will drop down another...can not get the car to upshift...left cold for 2-3 hours problem goes away...untill I get on the highway again.Had the transmission fluid flushed and the valves cleaned..would really appreciate some imput on this...Thanks

I dont know if this is the same but my 78 sl started to do down shift and then upshift in conditions I thought unusual. After about 2weeks it started slipping between 2nad and 3rd. I replaced the tranmission because of the clutches wearing. I would suggest looking into a vacuum leak also. Only a guess. Larry

Did you get any solutions to your troubles? I see by the lack of responses to your message that you did not gain satisfaction here, I wonder how you did in the garage? Do you have a huge bill in your pocket? The reason I ask is I just purchased a 560 SEL with 82000 kilometers (I assume they are the same transmission) I have first and second but there seems to be no grab in third. It looks like I am in the later stages of the problem you are describing. I think the clutches in mine are toast, I will be checking with shops tommorrow. I will let you know my miseries so we can commiserate.

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1987 560 SEL
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